Mobile terminals that support audio applications are becoming increasingly popular and, consequently, there is a growing demand for various audio communications applications. For example, some users may utilize Bluetooth-enabled devices, such as headphones and/or speakers, to allow them to communicate audio data with their wireless handset while freeing them to perform other activities. Other users may have portable electronic devices that may enable them to play stored audio content and/or receive audio content via FM broadcast communication, for example. Other users may use mobile terminals that have near field communication (NFC) capability.
Near field communication (NFC) is a communication technology that enables wireless communication devices, such as cellular telephones, SmartPhones, and personal digital assistants (PDAs) to establish peer-to-peer (P2P) networks. NFC may enable electronic devices to exchange data and/or initiate applications automatically when they are brought in close proximity, for example ranging from touching, or 0 cm, to a distance of about 20 cm. NFC may enable downloading of images stored in a digital camera, to a personal computer, or downloading of audio and/or video entertainment to MP3 devices, or downloading of data stored in a SmartPhone to a personal computer, or other wireless device, for example. NFC may be compatible with smart card technologies and may also be utilized to enable purchase of goods and services.
Near Field Communication (NFC) is a low speed communication protocol, which may be used, for example, to set up a Bluetooth communication link between two Bluetooth enabled devices by simply touching these two device to initiate a connection to exchange the parameters of the Bluetooth communication. A Bluetooth communication session may be established as a second step of this procedure without any human intervention. Once the communication session is established, the devices may be moved away from each other but the communication may continue via the Bluetooth communication session that was established previously. The same procedure may be used to establish a wireless link, for example, Bluetooth, or Wi-Fi, between two laptops or consumer electronics devices like TVs, laptop computers, PDAs, mobile phones, and/or SmartPhones.
The NFC protocol is based on a wireless interface in which there are two parties to the communication. Accordingly, the protocol may be referred to as a peer-to-peer communication protocol. The NFC protocol may be utilized to establish wireless network connections between network appliances and consumer electronics devices. The NFC interfaces operate in the unregulated RF band of 13.56 MHz. This means that no restrictions are applied and no licenses are required for the use of NFC devices in this RF band. Of course, each country imposes certain limitations on the electromagnetic emissions in this RF band. These limitations mean that, in practice, the distance at which the devices may connect with each other is restricted and this distance may vary from country to country. Operating distances of 0˜20 cm may be generally utilized for NFC. The bit rate=(Dxfc)/128, where D=2N and N=0 to 6. Data may be Manchester encoded using ASK modulation.
As may be the case with the devices sharing a single RF band, the communication is half-duplex. The devices may implement a “listen before talk” policy, in which a device first listens on the carrier frequency and start transmitting a signal only if no other transmitting device is detected. The NFC protocol distinguishes between an initiator and a target of the communication. Any device may be either an Initiator or a target. The initiator is the device that initiates and controls the exchange of data. The target is the device that answers the request from the Initiator. The NFC protocol also distinguishes between two modes of operation, namely, an active mode and a passive mode. NFC compliant devices may support both communication modes. In the active mode of communication, the initiator and target devices may generate their own RF field to carry the data. In the passive mode of communication, only one device may generate the RF field while the other device uses load modulation to transfer the data. The NFC protocol specifies that the Initiator is the device responsible to generate the RF field.
Communication using NFC protocol may be desirable since it provides some features that may not be found in other general-purpose protocols. First of all, it is a very short-range protocol. It supports communication at distances measured in centimeters. The devices may have to be touched or almost touched to establish the link between them. This has some important consequences. The devices may rely on the protocol to be inherently secured since the devices must be placed very close to each other. It is easy to control whether the two devices communicate by simply placing them next to each other or keeping them apart. The procedure utilized for establishing the protocol is inherently familiar to people, since if it is desirable to have two devices communicate, the two devices may be brought with range, of the order of centimeters, of each other. This allows for the establishment of a network connection between the devices to be completely automated and transparent. The whole process may appear as though the devices recognize each other by touch and connect to each other once touching occurs.
Another important feature of the NFC protocol is the support for the passive mode of communication. This is very important for the battery-powered devices since conservation of power may be a high priority. The NFC protocol allows such a device, like a mobile phone, to operate in a power-saving mode, namely, the passive mode of NFC. This mode does not require both devices to generate the RF field and allows the complete communication to be powered from one side only. Of course, the device itself will still need to be powered internally but it does not have to “waste” the battery on powering the RF communication interface.
Additionally, the protocol may be used in conjunction with other protocols to select devices and automate connection set-up. Parameters of other wireless protocols may be exchanged allowing for automated set-up of other, SNF longer-range connections. Using longer-range protocols like Bluetooth or Wireless Ethernet may require selecting the correct device out of the multitude of devices in the range and providing the right parameters for the connection. Using NFC may require the touch of one device to another.
However, collocating several mobile applications in a single mobile terminal may lead to some difficulties. For example, the various applications may operate in different frequency spectrums, and therefore may need different oscillator circuits. Support for the various oscillators may require extra power, which is already a scarce resource for a mobile device, as well as additional device count and related layout real estate. An output clock signal from an oscillator may pick up interfering signals from other clock signals from other oscillators.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.